1. Field of the Invention
The present invention relates to a diaphragm used for a speaker.
2. Description of the Prior Art
In order to reproduce the original sound accurately, it is essential that a diaphragm for a speaker repeat piston motions with its entire surface in the same phase without being distorted or deformed. It is well known that light (low density .rho.) diaphragms with high rigidity (high Young's modulus E) are better for this purpose. In other words, the higher the velocity of sound propagation (E/.sub.p).sup.0.5, the better. It is also known that internal losses in appropriate amounts produce better results.
A recent example of a diaphragm, which has as its objective increasing (E/.sub.p).sup.0.5, as mentioned above, uses high-rigidity carbon fiber or the like.
Although diaphragms such as described above are able to prevent large deflections, their rigidity is higher and the Q factor at their resonance point is sharper. Therefore, they present a problem in that their frequency characteristics are not flat. They peak in the middle to high frequency range.
Furthermore, the sound of secondary radiation of the normal mode, caused by resonant vibration of the material, dulls the reproduced sound, thus making it impossible to reproduce clear sound.
As described above, while conventional speaker diaphragms using carbon fiber with high rigidity or similar materials have excellent rigidity, they present difficulties in restraining resonance of the material, and thus are unable to achieve the desired characteristics.